Research On Performances Of Lithium-sulfur Batteries Based On NiO Composite Cathodes Material

Because lithium-ion batteries are becoming more and more difficult to satisfy people's energy requirements,lithium-sulfur batteries have caused continuous concern owing to the high specific capacity and high energy density,which provides a reference for the development of new energy system.However,the non-conductivity,volume expansion and intermediate polysulfide dissolution of sulfur cathodes are major technical barries to commercialization of lithium-sulfur batteries.In this thesis,we explored the electrochemical performance on composite materials of different components and structures comprehensively on the lithium-sulfur batteries,such as S@Ni O,S@GO/Ni O,S@C/Ni/Ni O composite cathode.The study contents are as follows.(1)The flower-like nickel oxide porous microspheres were prepared by a template-free hydrot hermal method,and the influence of different experimental factors on the morphology of nickel oxi de was studied,so as to find out the best experimental conditions for preparing nickel oxide microsp heres.Using Ni O as a carrier for supporting sulfur,a composite electrode of S@Ni O was prepared by the hot melting method.The electrochemical performance showed that when the sulfur content was about 60%,the initial specific capacity of S@Ni O composite was 1096.2 m Ahg^-1 with 0.2C cur rent rate and capacity was 237.8 m Ah g^-1 over 300 cycles.(2)The GO was compounded with flower-shaped Ni O microspheres to form the structure that graphene nanosheets carryed Ni O.The spatial structure is well when the mass ratio of GO to Ni O is1:20.The electrochemical performance showed that when composite electrode S@GO/Ni O charges and discharges at 0.5C constant-current density,has the initial specific capacity of 830.1 m Ah g^-1and capacity was lefted at 399.3 m Ah g^-1 after 200 cycles,the cycle performance is well.(3)The Ni O microspheres are immersed in the sericin solution,carbonized and then oxidized to form a C/Ni/Ni O composite material.S@C/Ni/Ni O composite electrode has the first discharge specific capacity of 1192.2 m Ahg^-1at a rate of 0.2 C and the capacity was 358.3 m Ah g^-1 over 200cycles.At 1C high constant-current,the capacity steadied at 286.3 m Ah g^-1 over 1000 cycles and with low attenuation rate of 0.068%,the capacity was 171.3 m Ah g^-1 lefted at 5 C.The electrochemical performance enhanced mainly because of the chemical adsorption between Ni O and polysulfides,and the presence of metallic nickel and sericin-derived carbon in S@C/Ni/Ni O which promote the conductivity of the material characteristic.Through the experimental research of this paper,the composition and structure of the lithium-sulfur battery positive electrode are modified,and the S@C/Ni/Ni O composite cathode shows better electrochemical properties,which supplys a better basis and idea for solving the issues faced by the sulfur cathode of lithium-sulfur batteries.